Brine the Chicken: Place the chicken breasts between two sheets of baking parchment and gently pound them to an even thickness of about 1.5cm. This ensures they cook evenly. In a medium bowl, whisk together the buttermilk and hot sauce. Add the chicken breasts, ensuring they are fully submerged. Cover and refrigerate for at least 1 hour, or up to 4.

Prepare the Coating & Sauce: While the chicken is brining, prepare the other components. In a wide, shallow dish, whisk together the plain flour, cornflour, smoked paprika, garlic powder, onion powder, cayenne pepper, salt, and black pepper. In a small bowl, mix the mayonnaise, sriracha, and lime juice for the spicy mayo. Cover and pop in the fridge.

Heat the Oil: Pour the oil into a large, heavy-bottomed saucepan or Dutch oven until it's about 5cm deep. Heat over a medium-high heat to 175°C. If you don't have a thermometer, you can test it by dropping a small cube of bread into the oil; it should turn golden brown in about 30-40 seconds.

Dredge the Chicken: Set up your dredging station. Take one piece of chicken from the buttermilk, letting the excess drip off. Dredge it thoroughly in the seasoned flour mixture, pressing down firmly to ensure it's completely coated. For an extra crispy crust, I find it's best to dip it back into the buttermilk briefly, and then dredge it in the flour a second time. This double-dredge method is explained well on sites like Serious Eats and it creates those lovely craggy bits. Place the coated chicken on a wire rack and repeat with the remaining pieces.

Fry the Chicken: Carefully place two pieces of chicken into the hot oil, ensuring not to overcrowd the pan. Fry for 4-6 minutes per side, turning once, until deep golden brown, crisp, and cooked through. The internal temperature should reach 74°C.

Rest the Chicken: Once cooked, remove the chicken from the oil using tongs and place it back on the wire rack to drain. Sprinkle immediately with a tiny pinch of extra salt. Let it rest for a couple of minutes while you fry the remaining two pieces.

Assemble Your Sandwich: Now for the best part! Toast your brioche buns. Spread a generous layer of the spicy mayo on the bottom bun. Top with some crisp lettuce, followed by the crispy chicken fillet, and finally, a few slices of dill pickle. Place the top bun on and serve immediately.